Particle-and droplet-laden flows are central to many problems in mechanics and transport.They occur in sedimentladen boundary layers,gas-solid and gas-liquid dispersions,and surface-water films driven by external forc...Particle-and droplet-laden flows are central to many problems in mechanics and transport.They occur in sedimentladen boundary layers,gas-solid and gas-liquid dispersions,and surface-water films driven by external forcing.They also underpin practical applications ranging from environmental transport to high-speed and aerothermal systems.Despite decades of progress,prediction remains difficult.The physics spans a wide range of scales and often couples turbulence,interphase momentum exchange,collisions,and interfacial transport.Reliable computation therefore requires both robust numerical methodology and careful physical interpretation.展开更多
The research presented in this paper aimed to analyze the evolution of fractures in strata in relation to the progress of longwall mining.To achieve this objective,an introscopic probe equipped with a highresolution c...The research presented in this paper aimed to analyze the evolution of fractures in strata in relation to the progress of longwall mining.To achieve this objective,an introscopic probe equipped with a highresolution camera was developed,along with additional equipment that enables continuous recording of the internal surfaces of drainage boreholes exceeding 100 m in depth.The probe was utilized to test two methane drainage boreholes in the Z-3b longwall,which operates within the 501/3 coal seam of the Jankowice mine in Poland.Automatic image analysis methods were applied to evaluate the recorded images,based on a newly developed classificationsystem for fractures categorized by size and number.The results were compared with an analysis of changes in the methane capture rate from the drainage boreholes,which correlated with longwall mining progress.A strong correlation was observed between the number of fractures and the lithology of the strata layers.The largest number of fractures and their evolution were recorded in the coal layers,followed by the shale layers,while the sandstone layers exhibited the least number of fractures.Based on parallel measurements of the methane capture rate from the drainage boreholes during the progress of longwall mining,the extent of the strata's fracture zone was determined to range from 6 m to 36 m.Within the fracture zone,the strata are highly fractured,which leads to an increase in methane emissions through seepage and diffusion processes.展开更多
Large-eddy simulation(LES)is conducted to study the statistical properties of mixed-phase turbulence induced by the breaking of bow waves in flow past a partially submerged plate.The simulation is performed using a fi...Large-eddy simulation(LES)is conducted to study the statistical properties of mixed-phase turbulence induced by the breaking of bow waves in flow past a partially submerged plate.The simulation is performed using a finite difference method,with the air-water interface captured by a coupled level-set and volume-of-fluid method.Four cases are conducted to investigate the effects of Froude number on turbulent statistics,including the mean velocity,turbulence kinetic energy,and turbulence mass flux(TMF),which is an additional unclosed term in the Reynolds-averaged momentum equation.The TMF,especially its vertical component,shows a complex behaviour with respect to the Froude number.This property of the TMF imposes high demands on the robustness of the closure model of TMF.The present LES data is further used to examine a closure model of the TMF production term,which shows a high correlation with the data obtained from LES.展开更多
Damage and failure due to distributed microcracks or microvoids are on the challenging frontiers of solid mechanics. This appeals strongly to tools not yet fully developed in continuum damage mechanics, in particular ...Damage and failure due to distributed microcracks or microvoids are on the challenging frontiers of solid mechanics. This appeals strongly to tools not yet fully developed in continuum damage mechanics, in particular to irreversible statistical thermodynamics and a unified macroscopic equations of mechanics and kinetic equations of microstructural transformations. This review provides the state of the art in statistical microdamage mechanics. (1) It clarifies on what level of approximation continuum damage mechanics works. Particularly,D-level approximation with dynamic function of damage appears to be a proper closed trans-scale formulation of the problem. (2) It provides physical foundation of evolution law in damage mechanics. Essentially, the damage-dependent feature of the macroscopic evolution law is due to the movement of microdamage front, resulting from microdamage growth. (3) It is found that intrinsic Deborah numberD *, a ratio of nucleation rate over growth rate of microdamage, is a proper indication of critical damage in damage mechanics, based on the idea of damage localization. (4) It clearly distinguishes the non-equilibrium damage evolution from equilibrium phase transition, like percolation.展开更多
The development of geotechnical plasticity is reviewed and some problems of applying the classical plastic mechanics (CPM) to geomaterials are analyzed, and then CPM’s three hypotheses not fitted the deformation mech...The development of geotechnical plasticity is reviewed and some problems of applying the classical plastic mechanics (CPM) to geomaterials are analyzed, and then CPM’s three hypotheses not fitted the deformation mechanism of geomaterials are pointed out. By giving up the three hypotheses, a generalized plastic potential theory can be obtained from solid mechanics directly, and then the traditional plastic mechanics can be changed to a more generalized plastic mechanics, namely generalized plastic mechanics (GPM). The GPM adopts the component theory as theoretical base, so it can reflect the influence of transition of stress path. The unreasonable phenomena such as excessive dilatancy caused by adopting the normality-flow law can be avoided, and the error caused by the arbitrary assumption of plastic potential surfaces cannot be produced. The yield surface theory, hardening laws and stress-strain relations of GPM are given, and a GPM including the rotation of principal stress axes is also established. It is pointed out that the yield condition is a state parameter as well as a test parameter, and it can only be given by test. After the practical application, it is shown that the GPM cannot only be applied to the modeling theory of geomaterials but also to other fields of geomechanics such as limit analysis.展开更多
The Micro- and Nano-mechanics Working Group of the Chinese Society of Theoretical and Applied Mechanics organized a forum to discuss the perspectives, trends, and directions in mechanics of heterogeneous materials in ...The Micro- and Nano-mechanics Working Group of the Chinese Society of Theoretical and Applied Mechanics organized a forum to discuss the perspectives, trends, and directions in mechanics of heterogeneous materials in January 2010. The international journal, Acta Mechanica Solida Sinica, is de- voted to all fields of solid mechanics and relevant disciplines in science, technology, and engineering, with a balanced coverage on analytical, experimental, numerical and applied investigations. On the occasion of the 30TM anniversary of Acta Mechanica Solida Sinica, its editor-in-chief, Professor Q.S. Zheng invited some of the forum participants to review the state-of-the-art of mechanics of heterogeneous solids, with a particular emphasis on the recent research development results of Chinese scientists. Their reviews are organized into five research areas as reported in different sections of this paper. ~I firstly brings in fo- cus on micro- and nano-mechanics, with regards to several selective topics, including multiscale coupled models and computational methods, nanocrystal superlattices, surface effects, micromechanical damage mechanics, and microstructural evolution of metals and shape memory alloys. ~II shows discussions on multifield coupled mechanical phenomena, e.g., multi-fields actuations of liquid crystal polymer networks, mechanical behavior of materials under radiations, and micromechanics of heterogeneous materials. In ~III, we mainly address the multiscale mechanics of biological nanocomposites, biological adhesive surface mechanics, wetting and dewetting phenomena on microstructured solid surfaces. The phononic crystals and manipulation of elastic waves were elaborated in ~IV. Finally, we conclude with a series of perspectives on solid mechanics. This review will set a primary goal of future science research and engineering application on solid mechanics with the effort of social and economic development.展开更多
The performance of the flexibility and stretchability of flexible electronics depends on the mechanical structure design,for which a great progress has been made in past years.The use of prestrain in the substrate,cau...The performance of the flexibility and stretchability of flexible electronics depends on the mechanical structure design,for which a great progress has been made in past years.The use of prestrain in the substrate,causing the compression of the transferred interconnects,can provide high elastic stretchability.Recently,the nonbuckling interconnects have been designed,where thick bar replaces thin ribbon layout to yield scissor-like in-plane deformation instead of in-or out-of-plane buckling modes.The nonbuckling interconnect design achieves significantly enhanced stretchability.However,combined use of prestrain and nonbuckling interconnects has not been explored.This paper aims to study the mechanical behavior of nonbuckling interconnects bonded to the prestrained substrate analytically and numerically.It is found that larger prestrain,longer straight segment,and smaller arc radius yield smaller strain in the interconnects.On the other hand,larger prestrain can also cause larger strain in the interconnects after releasing the prestrain.Therefore,the optimization of the prestrain needs to be found to achieve favorable stretchability.展开更多
The constants in fracture mechanics are fracture toughness(for plane strain),critical value of J—integral,critical value of crack tip opening displacement.Mechanical testing under certain conditions to determine them...The constants in fracture mechanics are fracture toughness(for plane strain),critical value of J—integral,critical value of crack tip opening displacement.Mechanical testing under certain conditions to determine them is used.They are complicated,long and expensive procedures.In practice,it is interesting to determine the constant in fracture mechanics for elements of constructions by means of non-destructive testing(NDT)(non-destructive evaluations,NDE)from Al+3.5%Mg alloys(according EN 1706).展开更多
The IP （inverse problem） in solid mechanics have emerged through the 20th century and measured. Nowadays has accept the classification of inverse problems in solid mechanics [1]： retrospective IP, boundary IP, coef...The IP （inverse problem） in solid mechanics have emerged through the 20th century and measured. Nowadays has accept the classification of inverse problems in solid mechanics [1]： retrospective IP, boundary IP, coefficient IP, geometric IP. The IPs in theory of elasticity, theory of plasticity, theory of strengthening, fatigue theory, fracture theory micro-structural of polycrystalline materials are formulated and solved. The method of high frequency theory of ultrasonic waves is used. The results which are obtained here show, that all coefficients and geometrical characteristics of imperfections in the material are functions only of longitudinal and transversal velocities and attenuation of ultrasonic waves, which are measured, according ASTM E 494： 2015. The received relationships from this article could be used for NDE （non-destructive evaluation） of the coefficients and the geometrical characteristics of imperfections in polycrystalline materials.展开更多
A newly developed P-doped CrCoNi medium-entropy alloy(MEA)provides both higher yield strength and larger uniform elongation than the conventional CrCoNi MEA,even superior tensile ductility to the other-element-doped C...A newly developed P-doped CrCoNi medium-entropy alloy(MEA)provides both higher yield strength and larger uniform elongation than the conventional CrCoNi MEA,even superior tensile ductility to the other-element-doped CrCoNi MEAs at similar yield strength levels.P segregation at grain boundaries(GBs)and dissolution inside grain interiors,together with the related lower stacking fault energy(SFE)are found in the P-doped CrCoNi MEA.Higher hetero-deformation-induced(HDI)hardening rate is observed in the P-doped CrCoNi MEA due to the grain-to-grain plastic deformation and the dynamic structural refinement by high-density stacking fault-walls(SFWs).The enhanced yield strength in the P-doped CoCrNi MEA can be attributed to the strong substitutional solid-solution strengthening by severer lattice distortion and the GB strengthening by phosphorus segregation at GBs.During the tensile deformation,the multiple SFW frames inundated with massive multi-orientational tiny planar stacking faults(SFs)between them,rather than deformation twins,are observed to induce dynamic structural refinement for forming par-allelepiped domains in the P-doped CoCrNi MEA,due to the lower SFE and even lower atomically-local SFE.These nano-sized domains with domain boundary spacing at tens of nanometers can block disloca-tion movement for strengthening on one hand,and can accumulate defects in the interiors of domains for exceptionally high hardening rate on the other hand.展开更多
In recent decades,capacitive pressure sensors(CPSs)with high sensitivity have demonstrated significant potential in applications such as medical monitoring,artificial intelligence,and soft robotics.Efforts to enhance ...In recent decades,capacitive pressure sensors(CPSs)with high sensitivity have demonstrated significant potential in applications such as medical monitoring,artificial intelligence,and soft robotics.Efforts to enhance this sensitivity have predominantly focused on material design and structural optimization,with surface microstructures such as wrinkles,pyramids,and micro-pillars proving effective.Although finite element modeling(FEM)has guided enhancements in CPS sensitivity across various surface designs,a theoretical understanding of sensitivity improvements remains underexplored.This paper employs sinusoidal wavy surfaces as a representative model to analytically elucidate the underlying mechanisms of sensitivity enhancement through contact mechanics.These theoretical insights are corroborated by FEM and experimental validations.Our findings underscore that optimizing material properties,such as Young’s modulus and relative permittivity,alongside adjustments in surface roughness and substrate thickness,can significantly elevate the sensitivity.The optimal performance is achieved when the amplitude-to-wavelength ratio(H/)is about 0.2.These results offer critical insights for designing ultrasensitive CPS devices,paving the way for advancements in sensor technology.展开更多
At present,noise reduction has become an urgent challenge across various fields.Whether in the context of household appliances in daily life or in the enhancement of stealth performance in military equipment,noise con...At present,noise reduction has become an urgent challenge across various fields.Whether in the context of household appliances in daily life or in the enhancement of stealth performance in military equipment,noise control technologies play a critical role.This study introduces a computational framework for simulating Helmholtz equationgoverned acoustic scattering using a boundary element method(BEM)integrated with Loop subdivision surfaces.By adopting the Loop subdivision scheme—a widely used computer-aided design(CAD)technique-the framework unifies geometric representation and physical field discretization,ensuring seamless compatibility with industrial CAD workflows.The core innovation lies in the novel integration of conditional generative adversarial networks(CGANs)into the subdivision surface BEM to assist and accelerate the numerical computation process.In this study,for the two cases examined,the results show that the CGAN-enhanced approach achieves substantial gains in computational efficiency without compromising accuracy.A hierarchical acceleration strategy is further proposed:the fast multipole method(FMM)first reduces baseline computational complexity,while CGAN-driven secondary acceleration and data augmentation enable real-time parameter exploration.Benchmark validations and practical engineering applications demonstrate the method’s robustness and scalability for large-scale structural-acoustic analysis.展开更多
The 40th anniversary of Acta Mechanica Sinica(AMS)marks a milestone of the journal and its incessant pursuit of novelty and excellence.AMS strives for publishing reports pushing the knowledge boundaries and breaking e...The 40th anniversary of Acta Mechanica Sinica(AMS)marks a milestone of the journal and its incessant pursuit of novelty and excellence.AMS strives for publishing reports pushing the knowledge boundaries and breaking engineering limits where mechanics plays a vital role.展开更多
This study introduces the“mineral-pore integration”paradigm to address unresolved challenges in understanding flow characteristics within heterogeneous tight oil reservoirs.By analyzing the complementary relationshi...This study introduces the“mineral-pore integration”paradigm to address unresolved challenges in understanding flow characteristics within heterogeneous tight oil reservoirs.By analyzing the complementary relationship between minerals and pore-fractures,we highlight the critical role of mineralogical composition in regulating fluid flow dynamics.Existing research has focused on the qualitative pore morphology and size characterization,neglecting the quantitative dependency between minerals and pore structures.To bridge this gap,we propose the development of quantitative discrimination models using machine learning algorithms to decode mineral-pore coupling mechanisms.Additionally,we advocate for multiscale experimental and numerical approaches,including multi-physics field coupling simulations and microscale visualization experiments,to quantify flow disparities in pores formed by different minerals(e.g.,feldspar,clay,carbonate).The integration of these methods aims to reveal novel flow behaviors,optimize displacement strategies,and enhance residual oil recovery.This framework provides a foundational basis for precise reservoir management by linking mineralogy to pore-scale flow mechanisms,offering actionable insights for tight oil exploitation.展开更多
The inelastic behavior of thermoplastic polymers may involve shearing and crazing,and both depend on temperature and strain rate.Traditional constitutive models account for temperature and strain rate through phenomen...The inelastic behavior of thermoplastic polymers may involve shearing and crazing,and both depend on temperature and strain rate.Traditional constitutive models account for temperature and strain rate through phenomenological or empirical formulas.In this study,we present a physics-guided machine learning(ML)framework to model shear and craze in polymeric materials.The effects of all three principal stresses for the craze initiation are considered other than the maximum tensile principal stress solely in previous works.We implemented a finite element framework through a user-defined material subroutine and applied the constitutive model to the deformation in three polymers(PLA 4060D,PLA 3051D,and HIPS).The result shows that our ML-based model can predict the stress-strain and volume-strain responses at different strain rates with high accuracy.Notably,the ML-based approach needs no assumptions about yield criteria or hardening laws.This work highlights the potential of hybrid physics-ML paradigms to overcome the trade-offs between model complexity and accuracy in polymer mechanics,paving the way for computationally efficient and generalizable constitutive models for thermoplastic materials.展开更多
The initial stresses widely exist in elastic materials.While achieving a continuum stress-free configuration through compatible unloading is desirable,mechanical unloading alone frequently proves insufficient,posing c...The initial stresses widely exist in elastic materials.While achieving a continuum stress-free configuration through compatible unloading is desirable,mechanical unloading alone frequently proves insufficient,posing challenges in avoiding virtual stress-free configurations.In this paper,we introduce a novel concept of equivalent temperature variation to counteract the incompatible initial strain.Our focus is on initially stressed cylindrical and spherical elastomers,where we first derive the Saint-Venant,Beltrami-Michell,and Volterra integral conditions in orthogonal curvilinear coordinates using the exterior differential form theory.It is shown that for any given axially or spherically distributed initial stress,an equivalent temperature variation always exists.Furthermore,we propose two innovative initial stress forms based on the steady-state heat conduction.By introducing an equivalent temperature variation,the initial stress can be released through a compatible thermo-mechanical unloading process,offering valuable insights into the constitutive theory of initially stressed elastic materials.展开更多
Voids play an important role in the fatigue behaviour of polycrystal materials.In this paper,the effects of three factors affecting the stress concentration factors(SCFs)near voids,i.e.,size,depth,and applied load,are...Voids play an important role in the fatigue behaviour of polycrystal materials.In this paper,the effects of three factors affecting the stress concentration factors(SCFs)near voids,i.e.,size,depth,and applied load,are investigated by employing crystal plasticity constitutive models in polycrystal bulks.The results indicate that SCF is dominated by the void size,while void depth and stress level play secondary roles.The SCF fluctuates by the orientation differences among grains and increases with increasing the size of the void.Finally,based on sensitivity examination of orientations and configurations of grains sur-rounding the void,an empirical multivariable-coupled formula is proposed to assess SCF near voids considering anisotropy,and the presented model is in good agreement with the simulation results.展开更多
In this study,we numerically investigate the rise of a Taylor bubble in a vertically oscillating round tube.The results show that increasing the oscillation frequency and amplitude reduces the bubble rise velocity,whi...In this study,we numerically investigate the rise of a Taylor bubble in a vertically oscillating round tube.The results show that increasing the oscillation frequency and amplitude reduces the bubble rise velocity,which is consistent with previously reported experimental findings.Analysis of the flow in the annular film region indicates that the influence of tube wall oscillations is minimal.This suggests that the effect of tube oscillations is essentially equivalent to that of an oscillating piston above the bubble,leading to a similar mechanism for bubble deceleration.Using a theoretical formula from the literature,we demonstrate that at sufficiently high frequencies,the amplitude of the tube velocity oscillations becomes the sole control parameter affecting bubble deceleration.This study enhances our understanding of Taylor bubble behavior in mechanically oscillating environments and provides useful insights into the design of control strategies for Taylor bubble motion in vertical slug flows.展开更多
The consistency of the dynamic behavior of the mechanical equivalent model of high-speed pantographs with that of actual high-speed pantographs under service conditions is crucial for the correctness and accuracy of t...The consistency of the dynamic behavior of the mechanical equivalent model of high-speed pantographs with that of actual high-speed pantographs under service conditions is crucial for the correctness and accuracy of the numerical simulation results of the pantograph-catenary interaction.Firstly,based on experimental data and the finite element method,models of a mass-point frame and reduced pan head were established,which can simulate the rolling and pitching motion characteristics of the dual-strip pan head.The correctness of the finite element numerical simulation of the pantograph-catenary system based on the model was verified through an industry standard and line tests.Then,the variation law of the standard deviation of the contact force(SDCF)in the speed range of 240-450 km/h was studied,and the mechanism of large fluctuation in SDCF was explained from the perspective of pantograph-catenary resonance.Finally,the influence of pan head degree of freedom and low-pass filtering frequency of the contact force time-domain signal on SDCF was studied,and the applicable speed level of the traditional three-mass model and 20 Hz filtering were provided.展开更多
文摘Particle-and droplet-laden flows are central to many problems in mechanics and transport.They occur in sedimentladen boundary layers,gas-solid and gas-liquid dispersions,and surface-water films driven by external forcing.They also underpin practical applications ranging from environmental transport to high-speed and aerothermal systems.Despite decades of progress,prediction remains difficult.The physics spans a wide range of scales and often couples turbulence,interphase momentum exchange,collisions,and interfacial transport.Reliable computation therefore requires both robust numerical methodology and careful physical interpretation.
基金the PICTO project(RFCR-CT-2018-800711)funded by the European Research Fund for Coal and Steel(RFCS)and the Polish Ministry of Science and Higher Education(W93/FBWiS/2018).
文摘The research presented in this paper aimed to analyze the evolution of fractures in strata in relation to the progress of longwall mining.To achieve this objective,an introscopic probe equipped with a highresolution camera was developed,along with additional equipment that enables continuous recording of the internal surfaces of drainage boreholes exceeding 100 m in depth.The probe was utilized to test two methane drainage boreholes in the Z-3b longwall,which operates within the 501/3 coal seam of the Jankowice mine in Poland.Automatic image analysis methods were applied to evaluate the recorded images,based on a newly developed classificationsystem for fractures categorized by size and number.The results were compared with an analysis of changes in the methane capture rate from the drainage boreholes,which correlated with longwall mining progress.A strong correlation was observed between the number of fractures and the lithology of the strata layers.The largest number of fractures and their evolution were recorded in the coal layers,followed by the shale layers,while the sandstone layers exhibited the least number of fractures.Based on parallel measurements of the methane capture rate from the drainage boreholes during the progress of longwall mining,the extent of the strata's fracture zone was determined to range from 6 m to 36 m.Within the fracture zone,the strata are highly fractured,which leads to an increase in methane emissions through seepage and diffusion processes.
基金supported by the National Natural Science Foundation of China(NSFC)Basic Science Center Program for‘Multiscale Problems in Nonlinear Mechanics’(Grant No.11988102)NSFC project(Grant No.11972038)Chinese Academy of Sciences Project for Young Scientists in Basic Research(Grant No.YSBR-087).
文摘Large-eddy simulation(LES)is conducted to study the statistical properties of mixed-phase turbulence induced by the breaking of bow waves in flow past a partially submerged plate.The simulation is performed using a finite difference method,with the air-water interface captured by a coupled level-set and volume-of-fluid method.Four cases are conducted to investigate the effects of Froude number on turbulent statistics,including the mean velocity,turbulence kinetic energy,and turbulence mass flux(TMF),which is an additional unclosed term in the Reynolds-averaged momentum equation.The TMF,especially its vertical component,shows a complex behaviour with respect to the Froude number.This property of the TMF imposes high demands on the robustness of the closure model of TMF.The present LES data is further used to examine a closure model of the TMF production term,which shows a high correlation with the data obtained from LES.
基金The project supported by the National Natural Science Foundation of China (19891180-02, 19972004) Major State Research Project (G200007735)
文摘Damage and failure due to distributed microcracks or microvoids are on the challenging frontiers of solid mechanics. This appeals strongly to tools not yet fully developed in continuum damage mechanics, in particular to irreversible statistical thermodynamics and a unified macroscopic equations of mechanics and kinetic equations of microstructural transformations. This review provides the state of the art in statistical microdamage mechanics. (1) It clarifies on what level of approximation continuum damage mechanics works. Particularly,D-level approximation with dynamic function of damage appears to be a proper closed trans-scale formulation of the problem. (2) It provides physical foundation of evolution law in damage mechanics. Essentially, the damage-dependent feature of the macroscopic evolution law is due to the movement of microdamage front, resulting from microdamage growth. (3) It is found that intrinsic Deborah numberD *, a ratio of nucleation rate over growth rate of microdamage, is a proper indication of critical damage in damage mechanics, based on the idea of damage localization. (4) It clearly distinguishes the non-equilibrium damage evolution from equilibrium phase transition, like percolation.
文摘The development of geotechnical plasticity is reviewed and some problems of applying the classical plastic mechanics (CPM) to geomaterials are analyzed, and then CPM’s three hypotheses not fitted the deformation mechanism of geomaterials are pointed out. By giving up the three hypotheses, a generalized plastic potential theory can be obtained from solid mechanics directly, and then the traditional plastic mechanics can be changed to a more generalized plastic mechanics, namely generalized plastic mechanics (GPM). The GPM adopts the component theory as theoretical base, so it can reflect the influence of transition of stress path. The unreasonable phenomena such as excessive dilatancy caused by adopting the normality-flow law can be avoided, and the error caused by the arbitrary assumption of plastic potential surfaces cannot be produced. The yield surface theory, hardening laws and stress-strain relations of GPM are given, and a GPM including the rotation of principal stress axes is also established. It is pointed out that the yield condition is a state parameter as well as a test parameter, and it can only be given by test. After the practical application, it is shown that the GPM cannot only be applied to the modeling theory of geomaterials but also to other fields of geomechanics such as limit analysis.
文摘The Micro- and Nano-mechanics Working Group of the Chinese Society of Theoretical and Applied Mechanics organized a forum to discuss the perspectives, trends, and directions in mechanics of heterogeneous materials in January 2010. The international journal, Acta Mechanica Solida Sinica, is de- voted to all fields of solid mechanics and relevant disciplines in science, technology, and engineering, with a balanced coverage on analytical, experimental, numerical and applied investigations. On the occasion of the 30TM anniversary of Acta Mechanica Solida Sinica, its editor-in-chief, Professor Q.S. Zheng invited some of the forum participants to review the state-of-the-art of mechanics of heterogeneous solids, with a particular emphasis on the recent research development results of Chinese scientists. Their reviews are organized into five research areas as reported in different sections of this paper. ~I firstly brings in fo- cus on micro- and nano-mechanics, with regards to several selective topics, including multiscale coupled models and computational methods, nanocrystal superlattices, surface effects, micromechanical damage mechanics, and microstructural evolution of metals and shape memory alloys. ~II shows discussions on multifield coupled mechanical phenomena, e.g., multi-fields actuations of liquid crystal polymer networks, mechanical behavior of materials under radiations, and micromechanics of heterogeneous materials. In ~III, we mainly address the multiscale mechanics of biological nanocomposites, biological adhesive surface mechanics, wetting and dewetting phenomena on microstructured solid surfaces. The phononic crystals and manipulation of elastic waves were elaborated in ~IV. Finally, we conclude with a series of perspectives on solid mechanics. This review will set a primary goal of future science research and engineering application on solid mechanics with the effort of social and economic development.
文摘The performance of the flexibility and stretchability of flexible electronics depends on the mechanical structure design,for which a great progress has been made in past years.The use of prestrain in the substrate,causing the compression of the transferred interconnects,can provide high elastic stretchability.Recently,the nonbuckling interconnects have been designed,where thick bar replaces thin ribbon layout to yield scissor-like in-plane deformation instead of in-or out-of-plane buckling modes.The nonbuckling interconnect design achieves significantly enhanced stretchability.However,combined use of prestrain and nonbuckling interconnects has not been explored.This paper aims to study the mechanical behavior of nonbuckling interconnects bonded to the prestrained substrate analytically and numerically.It is found that larger prestrain,longer straight segment,and smaller arc radius yield smaller strain in the interconnects.On the other hand,larger prestrain can also cause larger strain in the interconnects after releasing the prestrain.Therefore,the optimization of the prestrain needs to be found to achieve favorable stretchability.
文摘The constants in fracture mechanics are fracture toughness(for plane strain),critical value of J—integral,critical value of crack tip opening displacement.Mechanical testing under certain conditions to determine them is used.They are complicated,long and expensive procedures.In practice,it is interesting to determine the constant in fracture mechanics for elements of constructions by means of non-destructive testing(NDT)(non-destructive evaluations,NDE)from Al+3.5%Mg alloys(according EN 1706).
文摘The IP （inverse problem） in solid mechanics have emerged through the 20th century and measured. Nowadays has accept the classification of inverse problems in solid mechanics [1]： retrospective IP, boundary IP, coefficient IP, geometric IP. The IPs in theory of elasticity, theory of plasticity, theory of strengthening, fatigue theory, fracture theory micro-structural of polycrystalline materials are formulated and solved. The method of high frequency theory of ultrasonic waves is used. The results which are obtained here show, that all coefficients and geometrical characteristics of imperfections in the material are functions only of longitudinal and transversal velocities and attenuation of ultrasonic waves, which are measured, according ASTM E 494： 2015. The received relationships from this article could be used for NDE （non-destructive evaluation） of the coefficients and the geometrical characteristics of imperfections in polycrystalline materials.
基金supported by the National Key R&D Program of China(No.2019YFA0209902)the Natural Science Foundation of China(Nos.52071326,52192593,51601204)+1 种基金the NSFC Basic Science Center Program for Multiscale Problems in Nonlinear Mechanics(No.11988102)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB22040503).
文摘A newly developed P-doped CrCoNi medium-entropy alloy(MEA)provides both higher yield strength and larger uniform elongation than the conventional CrCoNi MEA,even superior tensile ductility to the other-element-doped CrCoNi MEAs at similar yield strength levels.P segregation at grain boundaries(GBs)and dissolution inside grain interiors,together with the related lower stacking fault energy(SFE)are found in the P-doped CrCoNi MEA.Higher hetero-deformation-induced(HDI)hardening rate is observed in the P-doped CrCoNi MEA due to the grain-to-grain plastic deformation and the dynamic structural refinement by high-density stacking fault-walls(SFWs).The enhanced yield strength in the P-doped CoCrNi MEA can be attributed to the strong substitutional solid-solution strengthening by severer lattice distortion and the GB strengthening by phosphorus segregation at GBs.During the tensile deformation,the multiple SFW frames inundated with massive multi-orientational tiny planar stacking faults(SFs)between them,rather than deformation twins,are observed to induce dynamic structural refinement for forming par-allelepiped domains in the P-doped CoCrNi MEA,due to the lower SFE and even lower atomically-local SFE.These nano-sized domains with domain boundary spacing at tens of nanometers can block disloca-tion movement for strengthening on one hand,and can accumulate defects in the interiors of domains for exceptionally high hardening rate on the other hand.
基金supported by the National Natural Science Foundation of China(Grant No.12272369)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB0620101).
文摘In recent decades,capacitive pressure sensors(CPSs)with high sensitivity have demonstrated significant potential in applications such as medical monitoring,artificial intelligence,and soft robotics.Efforts to enhance this sensitivity have predominantly focused on material design and structural optimization,with surface microstructures such as wrinkles,pyramids,and micro-pillars proving effective.Although finite element modeling(FEM)has guided enhancements in CPS sensitivity across various surface designs,a theoretical understanding of sensitivity improvements remains underexplored.This paper employs sinusoidal wavy surfaces as a representative model to analytically elucidate the underlying mechanisms of sensitivity enhancement through contact mechanics.These theoretical insights are corroborated by FEM and experimental validations.Our findings underscore that optimizing material properties,such as Young’s modulus and relative permittivity,alongside adjustments in surface roughness and substrate thickness,can significantly elevate the sensitivity.The optimal performance is achieved when the amplitude-to-wavelength ratio(H/)is about 0.2.These results offer critical insights for designing ultrasensitive CPS devices,paving the way for advancements in sensor technology.
基金the support from the 2025 Henan Provincial Science and Technology Research Project,the Zhumadian 2023 Major Science and Technology Special Projectthe Postgraduate Education Reform and Quality Improvement Project of Henan Province.
文摘At present,noise reduction has become an urgent challenge across various fields.Whether in the context of household appliances in daily life or in the enhancement of stealth performance in military equipment,noise control technologies play a critical role.This study introduces a computational framework for simulating Helmholtz equationgoverned acoustic scattering using a boundary element method(BEM)integrated with Loop subdivision surfaces.By adopting the Loop subdivision scheme—a widely used computer-aided design(CAD)technique-the framework unifies geometric representation and physical field discretization,ensuring seamless compatibility with industrial CAD workflows.The core innovation lies in the novel integration of conditional generative adversarial networks(CGANs)into the subdivision surface BEM to assist and accelerate the numerical computation process.In this study,for the two cases examined,the results show that the CGAN-enhanced approach achieves substantial gains in computational efficiency without compromising accuracy.A hierarchical acceleration strategy is further proposed:the fast multipole method(FMM)first reduces baseline computational complexity,while CGAN-driven secondary acceleration and data augmentation enable real-time parameter exploration.Benchmark validations and practical engineering applications demonstrate the method’s robustness and scalability for large-scale structural-acoustic analysis.
文摘The 40th anniversary of Acta Mechanica Sinica(AMS)marks a milestone of the journal and its incessant pursuit of novelty and excellence.AMS strives for publishing reports pushing the knowledge boundaries and breaking engineering limits where mechanics plays a vital role.
基金supported by Youth Innovation Promotion Association CAS,2023021,Shuheng DuYoung Elite Scientists Sponsorship Program by CAST,YESS20220094,Shuheng Du+2 种基金Young Elite Scientists Sponsorship Program by BAST,BYESS2023182,Shuheng DuBeijing Natural Science Foundation,8232054,Shuheng DuNational Natural Science Foundation of China,41902132,Shuheng Du.
文摘This study introduces the“mineral-pore integration”paradigm to address unresolved challenges in understanding flow characteristics within heterogeneous tight oil reservoirs.By analyzing the complementary relationship between minerals and pore-fractures,we highlight the critical role of mineralogical composition in regulating fluid flow dynamics.Existing research has focused on the qualitative pore morphology and size characterization,neglecting the quantitative dependency between minerals and pore structures.To bridge this gap,we propose the development of quantitative discrimination models using machine learning algorithms to decode mineral-pore coupling mechanisms.Additionally,we advocate for multiscale experimental and numerical approaches,including multi-physics field coupling simulations and microscale visualization experiments,to quantify flow disparities in pores formed by different minerals(e.g.,feldspar,clay,carbonate).The integration of these methods aims to reveal novel flow behaviors,optimize displacement strategies,and enhance residual oil recovery.This framework provides a foundational basis for precise reservoir management by linking mineralogy to pore-scale flow mechanisms,offering actionable insights for tight oil exploitation.
基金supported by the National Natural Science Foundation of China(NSFC)Excellent Research Group Program for“Multiscale Problems in Nonlinear Mechanics”(Grant No.12588201)。
文摘The inelastic behavior of thermoplastic polymers may involve shearing and crazing,and both depend on temperature and strain rate.Traditional constitutive models account for temperature and strain rate through phenomenological or empirical formulas.In this study,we present a physics-guided machine learning(ML)framework to model shear and craze in polymeric materials.The effects of all three principal stresses for the craze initiation are considered other than the maximum tensile principal stress solely in previous works.We implemented a finite element framework through a user-defined material subroutine and applied the constitutive model to the deformation in three polymers(PLA 4060D,PLA 3051D,and HIPS).The result shows that our ML-based model can predict the stress-strain and volume-strain responses at different strain rates with high accuracy.Notably,the ML-based approach needs no assumptions about yield criteria or hardening laws.This work highlights the potential of hybrid physics-ML paradigms to overcome the trade-offs between model complexity and accuracy in polymer mechanics,paving the way for computationally efficient and generalizable constitutive models for thermoplastic materials.
基金Project supported by the National Natural Science Foundation of China(Nos.12241205 and 12032019)the National Key Research and Development Program of China(No.2022YFA1203200)the Strategic Priority Research Program of Chinese Academy of Sciences(Nos.XDB0620101 and XDB0620103)。
文摘The initial stresses widely exist in elastic materials.While achieving a continuum stress-free configuration through compatible unloading is desirable,mechanical unloading alone frequently proves insufficient,posing challenges in avoiding virtual stress-free configurations.In this paper,we introduce a novel concept of equivalent temperature variation to counteract the incompatible initial strain.Our focus is on initially stressed cylindrical and spherical elastomers,where we first derive the Saint-Venant,Beltrami-Michell,and Volterra integral conditions in orthogonal curvilinear coordinates using the exterior differential form theory.It is shown that for any given axially or spherically distributed initial stress,an equivalent temperature variation always exists.Furthermore,we propose two innovative initial stress forms based on the steady-state heat conduction.By introducing an equivalent temperature variation,the initial stress can be released through a compatible thermo-mechanical unloading process,offering valuable insights into the constitutive theory of initially stressed elastic materials.
基金supported by the National Natural Science Foundation of China(Grant Nos.12022210 and 12032001)。
文摘Voids play an important role in the fatigue behaviour of polycrystal materials.In this paper,the effects of three factors affecting the stress concentration factors(SCFs)near voids,i.e.,size,depth,and applied load,are investigated by employing crystal plasticity constitutive models in polycrystal bulks.The results indicate that SCF is dominated by the void size,while void depth and stress level play secondary roles.The SCF fluctuates by the orientation differences among grains and increases with increasing the size of the void.Finally,based on sensitivity examination of orientations and configurations of grains sur-rounding the void,an empirical multivariable-coupled formula is proposed to assess SCF near voids considering anisotropy,and the presented model is in good agreement with the simulation results.
基金supported by the National Natural Science Foundation of China(Grant No.12202441).
文摘In this study,we numerically investigate the rise of a Taylor bubble in a vertically oscillating round tube.The results show that increasing the oscillation frequency and amplitude reduces the bubble rise velocity,which is consistent with previously reported experimental findings.Analysis of the flow in the annular film region indicates that the influence of tube wall oscillations is minimal.This suggests that the effect of tube oscillations is essentially equivalent to that of an oscillating piston above the bubble,leading to a similar mechanism for bubble deceleration.Using a theoretical formula from the literature,we demonstrate that at sufficiently high frequencies,the amplitude of the tube velocity oscillations becomes the sole control parameter affecting bubble deceleration.This study enhances our understanding of Taylor bubble behavior in mechanically oscillating environments and provides useful insights into the design of control strategies for Taylor bubble motion in vertical slug flows.
基金supported by the Major Project of China Railway Co.,Ltd.(Grant No.K2021J004-A)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB22020201)。
文摘The consistency of the dynamic behavior of the mechanical equivalent model of high-speed pantographs with that of actual high-speed pantographs under service conditions is crucial for the correctness and accuracy of the numerical simulation results of the pantograph-catenary interaction.Firstly,based on experimental data and the finite element method,models of a mass-point frame and reduced pan head were established,which can simulate the rolling and pitching motion characteristics of the dual-strip pan head.The correctness of the finite element numerical simulation of the pantograph-catenary system based on the model was verified through an industry standard and line tests.Then,the variation law of the standard deviation of the contact force(SDCF)in the speed range of 240-450 km/h was studied,and the mechanism of large fluctuation in SDCF was explained from the perspective of pantograph-catenary resonance.Finally,the influence of pan head degree of freedom and low-pass filtering frequency of the contact force time-domain signal on SDCF was studied,and the applicable speed level of the traditional three-mass model and 20 Hz filtering were provided.
